Depilatory



Patented Aug. 23, 1938 UNI-TED 1 STATES DEPILATORY Warren Moore, Bon Air, Va.

No Drawing. Application July 22, 1936, Serial No. 91,991

10 Claims.

My invention relates to a novel depilatory, and more particularly it relates to a depilatory which is effective in removing hair from the body without injury or irritation to the skin.

One object of my invention is to provide a depilatory which is selective in its action, softening or dissolving the hair substance and at the same time protecting the skin from injury or irritation by the active depilating agent.

A further object of the invention is to provide a depilatory composition comprising at least two liquid phases, one being a depilatory and the other being a lipin solvent noninjurious to the skin, in which composition the liquid phases possess wetting powers such that the depilatory will preferentially wet the hair, while the lipin solventwill preferentially wet the skin.

Still another object of the present invention is to furnish a depilatory of a plastic cream or salve-like constituency characterized by its rapid action on the hair and its freedom from deleterious action on the skin surfaces.

Other objects will be apparent from a consideration of the specification and claims.

The depilatories at present available rely for their action on an alkaline material, generally an alkaline sulphide or stannite. In order that the product will possess sufllcient potency to remove the hair from the surface of the skin, the alkalinity of these products cannot be reduced below a minimum, with the result that the product tends to cause irritation, and at times injury to the skin. The earliest depilatory mixtures were composed for the most part of orpiment and limefbut inrecent years the toxic arsenic compounds have been replaced by alkali or alkaline earth sulphides, or alkali stannites. In all these preparations, alkalinity sufficient to dissolve the hair substance is maintained which attacks the skin only slightly less rapidly. To minimize injury, the depilatory must be removed as soon as the hair is sufficiently softened.

There have been attempts to ameliorate these difficulties by the addition to the depilatory of so-called emollients, such as starch, dextrin,.

sugar, boroglyceride and the like, but this type of substance merely acts as a buffer, reducing the activity of the mixture toward both the hair. and the skin. Depilatories tend to follow the hair shaft into the follicle producing necrosis, and there is also a tendency'for the formation of ingrowing hairs when the hair shaft is destroyed below the level of the skin. These last two tendencies are encountered whether the emollients are present or absent and would also be present with'the types of depilatory products now employed even if some means were devised to render them noninjurious to the skin.

The depilatory of the present invention is characterized by the presence therein of a skin-protective liquid comprising a lipin solvent of particular properties, which liquid wets, and is spread over the skin before the skin is attacked by the active depilating solution. The depilatory contains at least two liquid phases, one of which preferentially wets the skin while the other preferentially wets the hair substance. The liquid phases are so interdispersed that the skin is contacted continuously or atclose intervals by its protective liquid and the hair is contacted continuously or at close intervals by the solution of depilatory agent. The nature of the two liquids is such that each functions in contact with its proper surface without impeding the function of the other. A product is thus provided which effectively protects the skin from the irritating and injurious action of the depilating agent without destroying the action of the depilating agent.

The skin-protective liquid of the type described may, in general, be associated with the depilatories now available, including those containing alkali and alkaline earth sulphides, alkali stannites or other active agents, and the product of the invention may be utilized in the form of a lotion, a paste, a salve, a cream, or the like. 'The skin-protective liquid may be mixed with the depilatory immediately before use, if desired, but preferably a product containing the two liquid phases will be manufactured and made available to the trade in the form of a single preparation. Preferably, the depilatory will be in the form of a cream or paste and will contain a hydrophile colloid such as finely divided magnesia, dolomitic lime, hydrated alumina, stabilized stannous hydroxide, proteins, or gums, although such a product may be obtained using starch, talc, or finishing lime, calcium oxalate and the like. If the solid material is not colloidal, a stable salve may be obtained by thorough mixing with the lipin solvent, especially with the aid of emulsifying agents. In such cases, the depilatory will contain the two liquid phases discussed and at least one solid phase. Other substances such as an oil-soluble water-insoluble wetting agent, an oleophile material, a perfume, and an emulsifying agent, may also be included in the product, as will be discussed hereinafter.

The skin-protective liquid is a lipin solvent, that is a substance which will dissolve or have an affinity for the -surface fat or oil of the skin with the result that it wets the skin, thus furnishing a protective coating. The lipin solvent may be a single liquid as the desired properties, or it may be a mixture of liquids, or of one or more solids dissolved in one or more liquids, which combination rmponds to the necessary qualifications. The lipin solvent employed in the depilatory is compatible with the depilatory mixture, but is of limited miscibility therewith. The compatibility of the lipin solvent is demonstrated by its stability in the product since compounds which react with the chemicals present in the mixture would not be available as a skin-protective agent at the-time of application of the depilatory. Thus, compounds whose properties are destroyed by saponification, reduction, or the formation of addition products do not provide a satisfactory product. The limited miscibility of the lipin solvent in the depilatory mixture provides the two liquid phases of the novel depilatory.

The lipin solvent selected for use will also coat the skin when, or immediately after, the preparation is applied, thus protecting it from the dipilating agent, and will possess a sufllciently low vapor pressure to remain on the skin during the action of the active agent. A lipin solvent having as high a spreading ability and as low a vapor pressure as possible is particularly applicable for use. The spreading action may, or may not, be indicated by the viscosity of the finished product, but in most instances, since a low viscosity favors the rapid coating of the skin, a viscosity as low as practicable is employed. The coating must be formed, to be effective, prior to the saponification of the superficial fat or oil film by the alkali of the mixture. For practical purposes, a lipin solvent which will function satisfactorily at all temperatures throughout the range where depilatories are ordinarily used (60 F.-98 F.) will be employed.

From a practical standpoint, the lipin solvent selected will be suiliciently non-toxic and nonirritating to the skin, and suiliciently free from toxic, irritating and malodorous vapors, to perform the function desired, and to render the depilatory acceptable to the user.

Hereinafter in the specification and claims, the skin-protective liquid will be defined as a substantially non-toxic non-irritating liquid lipin solvent compatible with the depilatory mixture and of limited miscibility therewith and possessing a sumciently high wetting power to wet the skin rapidly, and a suillciently low vapor pressure to remain thereon during the action of the depilatory".

The two liquid phases discussed form a colloidal system and the lipin solvent may-be dispersed in the depilating solution or the depilating solution may be dispersed in the lipin solvent. Preferably, for most purposes, the lipin solvent will be in the dispersed phase, since otherwise there is some tendency for the lipin solvent to coat both the skin and the hair, interfering with the action of the depilatory. The action of the depilatory of the present invention is dependent to an extent on the size of the dispersed droplets of the lipin solvent, since, if the droplets are too small, they tend to become immobilized on stabilized and will not satisfactorily wet the surface of the skin, and if they are too large, they tend to enclose portions of the hair, retarding the action of the depilatory. While the exact size of the droplets may vary over a wide range, the droplets should, in general, be larger than those of colloidal dimensions and few, if any, should exceed .5 millimeters in diameter. The molt satisfactory droplet size will vary according to the composition of the mixture and, as an example, a satisfactory preparation is provided when the majority of the droplets is in the neighborhood of .05 millimeters to .25 millimeters in diameter, although a few larger droplets, for example .5 millimeters in diameter, may be present.

The amount of lipin solvent present in the depilatory will depend on the particular use for which the product is designed but, in general, the lower limit for effective application is 1 In some instances, the lipin solvent will comprise 50% or more of the depilatory; for instance, in the preparation of a. shaving cream, the percentage may be relatively high. In most products, there will be present between 5% and 33%% of lipin solvent, and generally, the solvent will make up in the neighborhood of 10% of the total weight of the mixture. A satisfactory product for general use is provided when each cubic millimeter contains droplets between .06 and .2 millimeters in diameter.

From the above discussion, it will be realized that a large number of organic liquids, or of mixtures thereof, or of liquid mixtures of a solid and liquid, will possess the necessary properties and will be suitable for use. As examples of lipin solvents which are particularly applicable, the organic liquids having the desired properties may be selected from the class of solvents consisting of the middle range hydrocarbons, especially those containing the straight chain, aliphatic type; the higher ketones; and the higher ethers.

Undecane, tridecane, isomers of those products,

kerosene, naphtha, toluene, butyrone, n-caprone, methyl hexyl ketone and specially treated hydrocarbons are examples of the lipin solvents which may be used.

It has beendemonstrated that the normal or straight chain hydrocarbons, possessing a sumciently low vapor pressure to remain between theskln and the depilating agent, are especially satisfactory for use. These solvents possess the lowest viscosity (or highest mobility) and the lowest vapor pressure of any of the commonly available products. They are also non-toxic and non-irritating to the skin and are characterized by great chemical stability and a slight, pleasant odor. They may be obtained from various sources, for example they may be synthesized or may be obtained from petroleum, particularly from crudes of the Pennsylvania type. Since it is not necessary to use the pure hydrocarbon and suitable mixtures containing isomers or other materials are applicable, the hydrocarbons are preferably obtained from petroleum. A petroleum crude is preferably selected with a high content of materials having the desired properties, and the other materials, such as the aromatic hydrocarbons, the naphthenes, and the branched chain aliphatic hydrocarbons, are reduced in amount, or removed by appropriate refining processes, such as by distillation followed by treatment with chemicals or solvents.

For example, commercial kerosene obtained from Pennsylvania crude oil is subjected to a distillation process and a cut boiling between C. and 228 C. is collected. This distillate is purified by treatment with hot concentrated sulphuric acid. Thereafter, the distillate may be washed with caustic soda solution, followed by,

water. In a typical run, 100 c. c. of the distillate is heated to 100 C. in a boiling water bath and agitated for fifteen minutes with c. c. concentrated sulphuric acid, maintaining the temperature at or near 100 C. The acid is drawn off and the treatment is repeated. The oil is then washed with a small amount of water, followed by a solution of caustic soda to neutralize any sulphuric acid present, and finally with water again. The resulting product is colorless, boils between 150 C. and 228 C., and has a slight characteristic odor and a viscosity at ordinary temperature (23 0.), about equal to that of water at the same temperature. The hot acid treatment described introduces traces of "oilsoluble sulphonates into the product, the presenceof which may be advantageous, as will hereinafter appear. The product obtained is for conv/enience designated herein as Hydrocarbon A.

The mixture of hydrocarbons possessing the properties of the lipin solvent described may also be obtained by numerous other proceduresknown to the petroleum industry. It is recognized by the industry that different raw materials require different treatments and that the viscosity of hydrocarbon mixtures increases withtheir boiling points and with their chemical reactivity. For a given boiling range, viscosities can be reduced by drastic chemical treatments, for example with hot concentrated or fuming sulphuric acid or with sulphuric and chromic acids, and as pointed out previously minimumviscosity for a given boiling range is attained when the normal or straight chain hydrocarbons predominate. Thus, the product obtained by the above described process can be improved as to mobility by more drastic chemical treatment, and the boiling point may be varied widely without destroying the usefulness of the product. It is not to be understood from the above discussion that a physical or chemical treatment is always required, since highly efficient depilatories may be obtained using products of commerce, such as naphtha, preferably of the higher boiling types, or kerosene, as the lipin solvent.

The presence of oil-soluble, water-insoluble wetting agents in the depilatory augments the wetting power of the lipin solvent. Among the oil-soluble wetting agents are the oil-soluble sulphonates, oil-soluble soaps, and the higher ketones, such as camphor and cedrone. The oilsoluble wetting agents may be present in the lipin solvent or may be added thereto or to the depilatory mixture. fHydrocarbon A described above contains a small amount of these oil-soluble sulphonates which result from the treatment of the distillate with sulphuric acid. These wetting agents permit the use of smaller oil droplets in the depilatory mixture since the effectiveness of the product from the standpoint of its ability to wet the skin is increased. In general, the amount of oil-soluble wetting agent employed will be small, but relatively large amounts are not deleterious. In most instances where these compounds are employed, they will be present in amountsvaryi be increased in a paste or salve depilatory without destroying the consistency thereof. Aluminum stearate, magnesium laurate, high melting paramns ceresine, and carnauba wax are exam- "ples of substances of this type. These compounds tend to form water in oil dispersions. They may increase the viscosity of the oil by partial solution or colloidal dispersion, or they may concentrate at the interface between water and oil. reducing the mobility of the oil, increasing the mobility of the mixture or producing other effects. The amount used will depend on the substance and on the effect desired. Colloids may produce profound effects in minute quantities. Non-colloids used to absorb the oil are employed in larger amounts. In most instances the amount used will be between .1% and 50% based on the weight of the lipin solvent.

Unsaturated substances, and especially colloids dispersed in the lipin solvent, may be beneficial in that they may increase the adhesiveness and cohesiveness of the film of lipin solvent coating the skin. Examples of substances which can be dispersed colloidally' are rubber, gutta percha, and carnauba wax. Their addition may at the same time produce objectionable effects, such as increased viscosity, instability of the emulsion, etc. In consequence, they must be added with caution and their objectionable effects compensated as far as possible by adding substances having the reverse effects. For example, a tendency toward instability of mixtures in which the lipin solvent forms the dispersed phase is overcome by the presence of such emulsifying agents as primary alcohols and alkali soaps. Depilatories are particularlylikely to cause injury where the growth of hair is dense, as on a man's face or in the arm pits. Mixtures containing colloids have given superior protection on such areas. Relatively small amounts of these colloids, for example, between'0.1% and 3% based on the weight of the lipin solvent. are usually employed. The viscosity of lipin solvents containing colloids may be considerablyhigher than is ordinarily desirable.

Other organic materials also influence the properties of the depilatory. Substances which are liquid, or become liquid in the depilatory mixture, and which concentrate at the interface generally decrease the interfacial friction, increasing the fluidity of the'mixture, examples of such compounds being alcohols (cetyl alcohol), soap (sodium oleate), ketones (cedrone). Solids which concentrate at the interface, however, have the reverse efiect. Primary alcohols and alkali soaps, gums. and other hydrophile colloids which favor the oil in water dispersions aid in taking up large quantities of oil and the formation of small droplets. Tertiary alcohols (tertiary amyl, cyclohexanol and colesterol), and soaps of bivalent or polyvalent metals, however, tend to form water in oil dispersions, and their presence in oil in water dispersions may decrease the absorbtion of oil and increasethe drop size.

Water-soluble wetting agents may be employed, if care is taken to select a compound (and to use such proportions thereof) which will not prevent the lipin solvent from functioning as described. For example, the addition of small amounts of such wetting agents to a depilating agent containing an alkaline earth sulphide facilitates the displacement of oil from contact with the hair. Such substances as soaps, organic bases, alcohols, water-soluble sulphonates may be mentioned as examples.

Perfumes of the type used in depilatories are likely to contain substances which tend to increase, and substances which tend to decrease the drop size. Protracted agitation brings about a fractionation of these components which results in the formation of minute and large drops with relatively few drops of the intermediate desired size. This difllculty is overcome by using a-minimum of perfume, and by stopping the agitation when drops of the desired size are obtained.

The general influence on the depilatory of the present invention by the presence therein of various types of compounds has been indicated, and a colloidal chemist will have no difllculty in compounding a depilatory possessing the desired properties and functioning to provide a film of lipin solvent upon the skin to protect it from injury or irritation by the depilating agent.

The delipatory of the invention may be produced by various methods by which the various ingredients are intimately brought together to form the finished product in which there are present the two liquid phases in such physical condition that each will function as described. When the delipatory contains the solid phase as well as 'the two liquid phases, the presence of the lipin solvent improves the consistency and stability of the salve-like product. sulphide products containing the lipin solvent also have less sulphide odor than comparable products of the prior art.

In general, precautions should be taken to prevent the introduction of air into the products. The oxygen tends to weaken the depilatory and the nitrogen affects the consistency of the product,

rendering it dimcult to obtain a uniform product.

Eztample I A depilatory is prepared, using 45 c. c. of 0.6 m. sodium sulphide solution, 8 grams magnesium oxide, and 10 c. c. of "Hydrocarbon A and the mixing is accomplished by driving the lipin solvent into the plastic mass of magnesium oxide and sulphide solution through small orifices. This may be accomplished by flowing the oil through a rotating hollow shaft having a bulbat the bottom from which the lipin solvent escapes into the mass through small equatorial holes, (for example, 1 mm. in diameter), meanwhile bringing fresh portions of the mass into contact with the bulb by means of an independent stirring device or by moving the containing vessel. The magnesia is added to the depilatory solution in the vessel with or without the use of a layer of oil. The lipin V solvent is introduced through the rotating hollow shaft, the mixer being in motion. When all the oil has been poured into the shaft and driven into the mass by centrifugal force, a sample is examined. The size of the exit holes, the rate of rotation of the shaft and the mixer, the temperature, and the design of the apparatus determine,

for any composition, the sizes of the oil droplets.

A satisfactory combination of these factors to obtain the sizes desired may easily be determined by a few trial uses. Excessively large droplets can be eliminated by running the mixer slowly for some time, as they are thus brought to the surface where they break, permitting the free oil to be poured off. A microscopic examination of the product made as described showed the presence in .9 cubic millimeter of oil droplets as follows:

Less than .05 mm. lineal dimension Very many Between .05-.1 mm. lineal dimension 100 Between .1-.25 mm. lineal dimension 17 The product is particularly satisfactory for rapid removal of superfluous hair from the limbs over the entire temperature range, and the skin is completely protected from irritation and injury.

Example II In a 100 c. 0. tall beaker, 40 c. c. of approximately M/2 sodium sulphide solution and 10 c. c. of Hydrocarbon A" are placed, and 8.5 grams of light magnesium oxide is added slowly. The air is expelled from the powder as it settles through the oil. The mixture is allowed to stand until the magnesium oxide is hydrated and a thick salve containing free oil is obtained. The mixture is stirred with an impeller having a slight pitch at about 1200 R. P. M., the speed being sufliclent tobreak the oil into fine droplets but not sufllcient to carry air into the mixture. As soon as the oil is taken up, the agitation is stopped and a sample of the product is examined under a microscope. The droplets are counted, and 100 droplets between .06 mm. and 0.2 mm. in 1 cubic millimeter are a satisfactory number. Larger droplets should for the most part be absent and if the droplet size is not satisfactory, additional stirring will result in the desired product. The product obtained removes hair rapidly (2-3 minutes) from the limbs, and normal skin is protected from injury.

Example Ila In order to increase the wetting'power of the lipin solvent of Example II, 20 grams of mahogany soap is dissolved in 40 c. c. of Hydrocarbon A. The mixture is washed with caustic soda solution to remove any water-soluble substances. About 1% of this solution is added to Hydrocarbon A employed in Example II and, if desired, 1% of camphor or other ketone of that type is also added. Small amounts of cetyl alcohol may also be added. The lipin solvent is then mixed with the other ingredients as set forth in Example II, care being taken not to continue the agitation to the point where all the droplets are extremely small and relatively large with an absence of the desired intermediate size.

Example III In place of using a hydrophile colloid such as magnesium oxide, powdered materials may be incorporated with the depilating agent and the lipin solvent to form a paste or salve. The use of an emulsifying agent is recommended. In a typical case, 10 c. c. of Hydrocarbon A, .5 gram of purified mahogany soap, 10 grams of finishing lime, and 10 c. c. of M/2 sodium sulphide solution are thoroughly mixed together in a mortar by means of a pestle. The methods described in the preceding examples can also be used.

Example IV In an example where an alkaline earth sulphide is used, 40 c. c. of barium sulphide solution saturated at 23 C., 20 c. c. of Hydrocarbon A, 8 grams of ceresine, 8.5 grams of light magnesium oxide, and 1 drop of perfume are employed. The magnesium oxide is added to the oil and sulphide solution in the same manner as in Examples I or II. When the magnesium oxide has become hydrated, the ceresine is added and the mixture is warmed until the. ceresine melts and mixes with the oil. The mixture is stirred while hot for about five minutes with an impeller rotating at about 1450 R. P. M. The prod- 'uct is allowed to-cool and most of the ceresine precipitates.

in three-five minutes to a condition such that no resistance is offered to the razor. The skin is completely protected from irritation and in- E'mmple 1/ .several'times with caustic soda solution. After these two solutions are prepared, 40 c. c. of the stannite solution, 10 c. c. of Hydrocarbon A, and .1 c. c. of the oil-soluble sulphonate solution are added to a beaker. Then 8.5 grams of light magnesium oxide are added, and after standing for about two hours, the mass is stirred until the product has the correct consistency. A sample of .3 cubic millimeters was examined microscopically and 28 droplets of lipin solvent .1 to .2 millimeters and l droplet .2 to .4 millimeters were observed. The product removed hair on the limbs in two-three minutes with no irritation or injury to the skin. This is to be compared to the same depilatory in which there is present no lipin solvent, which causes severe cautery of the skin in five minutes.

Example VI A mixture of 40 c. c. of the stannite solution Egepared in accordance with Example V is mixed described in that example with '7 c. c. butyrone, and 8.5 grams of light magnesium oxide, and .1 gram of water-soluble sulphonate. The product removes hair in three-four minutes and the skin is protected from injury and irritation during the action of the depilatory. Due to the volatility of the butyrone, there is a tendency for it to evaporate after the softening of the hair, which can be overcome by the use of caprone in place thereof, or in admixture therewith.

Example VII Commercial deodorized kerosene ("ultrasene") 10 c. c. unvulcanized rubber .03 grams, cetyl alcohol .2 grams, commercial depilatory perfume 0.1 c. c. are mixed together until a solution of the ingredients is obtained. The rubber is conveniently dispersed in the solvent by soaking for several hours, heating over a water bath and triturating the rubber until dispersion is eflected.

The depilating agent consists of M/5 sodium sulphide solution and 40 c. c. of this solution is taken' up on 8.5 grams of light magnesium oxide. The two solutions are mixed as in Example If until a proper consistency is obtained. Droplets in this instance may be rather small, for example, in the neighborhood of 0.1 millimeter. The viscosity of the lipin solvent used in this example is about five times the viscosity of water and is, therefore, higher than in the other examples. The resulting product is especially adapted for ace on the beard as a brushless shaving prepara- Considerable modification is possible in the depilating agent and lipin solvent employed, as well as in the proportions thereof and in the choice and proportions of other materials used in theproduct, without departing from the essential features of the invention.

I claim:

1. A depilatory comprising a system of at least two liquid phases one dispersed in the other, one

of which liquid phases upon application of the depilatory preferentially wets the hair substance and exerts a depilating action thereon which phase comprises an aqueous solution of a depilating agent, and the other of which liquid phases upon application of the depiiatory preferentially wets the skin and serves as a protection to the skin which phase comprises a substantially nontoxic and non-irritating liquid lipin solvent compatible with the depilating solution and of limited miscibility therewith and possessing a sumciently high wetting power and a sufficiently low volatility to spread over the skin rapidly and to remain thereon while the dipilatory is in contact with the skin to afford protection of the skin from the irritating action of the depilating agent.

2. The depilatory of claim 1 wherein there is dispersed in the lipin solvent, an oleophile colloid.

3. A depilatory of salve-like consistency comprising a system of at least one solid phase comprising finely divided material having hydrophilic properties in admixture with at least two liquid phases one dispersed in the other, one of which liquid phases upon application of the depilatory preferentially wets the hair substance and exerts a depilating action thereon which phase comprises an aqueous solution of a depilating agent, and the other of which liquid phases upon application of the depilatory preferentially wets the skin and serves as a protection to the skin which phase comprises a substantially non-toxic and non-irritating liquid lipin solvent compatible with the depilating solution and of limited miscibility therewith and possessing a sufliciently high wetting power and a suillciently low volatility to spread over the skin rapidly and to remain thereon while the depilatory is in contact with the skin to aflord protection of the skin from the irritating action of the depilating agent.

4. The depilatory of claim 3 wherein the lipin solvent is present in amounts between 5% and of the total weight thereof.

5. The depilatory of claim 3 wherein the lipin solvent is in the dispersed phase and the majority of the dispersed droplets are of a size to wet the skin surface without interfering with the wetting of the hair by the depilating solution.

6. The depilatory of claim 3 wherein the lipin 10. A depilatory of salve' like consistency com prising an inorganic, finely divided material having hydrophilic properties in admixture with an aqueous solution of a depilating agent and a substantially non-toxic and non-irritating liquid lipin solvent compatible with the depilating solution and of limited .miscibility therewith, the said lipin solvent being dispersed in the aqueous solution, and being present in amounts of from 1%% to 50% by weight based on the total weight of the depilatory.

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